Synthesis And Photoelectric Properties Of Transition Metal Sulfides/graphene Composite Film

Platinum(Pt)is the most commonly used counter electrode material in dye-sensitized solar cell(DSSC)due to its high eletrocatalytic activity to the reduction of I3-to I-.However,Pt is expensive,rare and can be easily corroded by electrolyte,which greatly affect the stability of CE and hinder the industrialization development of DSSC.So people payed great attention to find the substitute of Pt.As transition metal chalcogenides have good catalytic activity and are abundant in nature,they have been a hot area for several years.In addition,we combined the transition metal chalcogenides and graphene to improve the performance of materials,because the novel two-dimensional graphene possesses record electrical conductivity and large specific surface area.The main contents and results of this research are as follows:MoS2/rGO composite film was successfully grown on FTO substrate by an all electrochemical strategy,which can directly act as CE of the DSSC without needing additional post-treatment.The proposed electrochemical strategy is very facile and quick,which just needs a few minutes to synthesize composite CE.The SEM and TEM research indicates that MoS2 has morphology of nanoparticles.The pre-prepared graphene film can promote the growth of MoS2 and makes the surface of composite films exhibit a 3D structure,which can improve the diffusion abilities of electrolyte.Cyclic voltammetry(CV)study shows that MoS2/rGO-CE owns a relatively low Epp and high reduction current density,which indicates that the composite CE have better catalytic abilities.In addition,the Rct of MoS2/rGO-CE got by EIS experiment is lower than that of MoS2-CE.It reveals the facile charge transfer between electrolyte and MoS2/rGO-CE.We changed the deposition time of graphene to get the optimized performance of the composite CE.When the deposition time of graphene is 80 s,it would reach optimal power conversion efficiency(PCE)of 8.01%.What's more,the composite CE based DSSC has a good stability as the PCE of it has no obvious change after several measurements.The MoS2/rGO-CE has a great mechanical property and can be tightly adhered to FTO substrate.All this excellent performance verifies the effectiveness of the all electrochemical strategy and the composite material after introducing the graphene.The FeS2/rGO composites were synthesized by a one plot hydrothermal method and applied to the CE of DSSC for the first time.The SEM and TEM tests show that FeS2 particles are connected by graphene,which can improve the charge transfer abilities of the composite material.CV test also shows that the FeS2/rGO-CE has a smaller Epp and bigger current density than that of FeS2-CE and even Pt-CE.It means that the composite CE has better electrocatalytic abilities than pure FeS2 and Pt CEs.J-V tests verify the results of CV tests.The PCE of FeS2/rGO-CE based DSSC comes to 8.53%,which is higher than that of FeS2-CE based DSSC(7.41%)and Pt-CE based DSSC(8.21%).In addition,the open-circuit voltage,short-density current density and fill factor of FeS2/rGO-CE based DSSC are 0.74V,17.6 mA and 65.01%,respectively.All this excellent photovoltaic performance parameters of composite material based DSSC indicate that the introducing of graphene improves the catalytic abilities of the FeS2/rGO CE.